The present invention relates to a ferroelectric memory device and a method of manufacturing the same.
A ferroelectric memory (FeRAM) retains data by spontaneous polarization of a ferroelectric film used in capacitor sections. Conventionally, the capacitor sections are formed by dry etching using a reactive gas with a patterned photoresist as a mask.
Since the materials for forming the capacitor sections, in particular, platinum (Pt) and iridium (Ir) suitably used as the electrode materials exhibit low reactivity to etching gas, conventional technology has employed etching with an increased physical effect (sputter etching). In this case, by-products produced during etching are not removed in the vapor phase but are redeposited on the side wall of the resist pattern. It is very difficult to remove these redeposited by-products, which remain as a structure. As a method for preventing redeposition of by-products on the side wall of the resist pattern, a method of etching while moving the resist backward has been proposed. However, this etching method causes the side wall of the capacitor section to be sloped, whereby a high degree integration becomes difficult.
The present invention has been achieved to solve this problem. An object of the present invention is to provide a ferroelectric memory device which can be manufactured with high accuracy, and a method of manufacturing the same.
(1) The present invention provides a method of manufacturing a ferroelectric memory device provided with a capacitor section having a structure in which a first electrode, a ferroelectric film, and a second electrode are deposited, the method comprising the steps of:
forming a first region having surface characteristics allowing a material for forming at least one of the first electrode, the ferroelectric film, and the second electrode of the capacitor section to be preferentially deposited, and a second region having surface characteristics allowing a material for forming at least one member of the capacitor section to be less deposited than the first region; and
providing the material for forming at least one member of the capacitor section to selectively form the member in the first region.
According to the present invention, at least one member of the capacitor section can be selectively formed in the first region, but is less formed in the second region. Therefore, at least one of the first electrode, the ferroelectric film, and the second electrode can be formed without etching.
(2) In this method of manufacturing a ferroelectric memory device, the first region and the second region may be formed on the surface of a base.
According to this configuration, at least one member of the capacitor section can be selectively formed on the surface of the base. In particular, degradation of the ferroelectric film can be reduced by applying the present invention when forming the first electrode and the second electrode, thereby easily achieving miniaturization of devices.
(3) In this method of manufacturing a ferroelectric memory device,
the first electrode may be formed in the first region of the base by forming a layer of an electrode material on the base,
the ferroelectric film may be formed on the first electrode by forming a layer of a ferroelectric material on the base, and
the second electrode may be formed on the ferroelectric film by forming a layer of an electrode material on the base.
This enables the first electrode, the ferroelectric film, and the second electrode to be formed on the surface of the base in that order, whereby layers of all these members can be formed selectively.
(4) In this method of manufacturing a ferroelectric memory device,
the surface of the base may be exposed in the first region, and
a surface of the second region may be a surface-modifying film of which affinity to the electrode materials and the ferroelectric material is lower than an affinity of the exposed surface in the first region.
According to this configuration, affinity to the electrode materials and the ferroelectric material in the first region can be relatively increased by decreasing the affinity to the electrode materials and the ferroelectric material in the second region.
(5) This method of manufacturing a ferroelectric memory device may further comprise a step of removing the surface-modifying film after forming the first electrode, the ferroelectric film, and the second electrode.
(6) In this method of manufacturing a ferroelectric memory device,
the surface-modifying film may be formed on the base and selectively removed in a region which becomes the first region to form the surface-modifying film only in the second region.
(7) In this method of manufacturing a ferroelectric memory device,
the first electrode may be formed on the surface of the base, and a layer of the ferroelectric material is formed on the base and the first electrode,
the first region and the second region may be formed on the surface of the formed ferroelectric material, and
the second electrode may be formed in the first region by forming a layer of the electrode material on the formed ferroelectric material.
This enables the electrode material to be selectively formed on the surface of the formed ferroelectric material.
(8) This method of manufacturing a ferroelectric memory device may further comprise a step of removing the formed ferroelectric material in the region other than the second region after forming the second electrode.
(9) In this method of manufacturing a ferroelectric memory device,
the surface of the formed ferroelectric material may be exposed in the first region, and,
a surface of the second region may be a surface-modifying film of which affinity to the electrode material is lower than an affinity of the exposed surface of the formed ferroelectric material in the first region.
According to this configuration, affinity to the electrode material in the first region can be relatively increased by decreasing the affinity to the electrode material in the second region.
(10) In this method of manufacturing a ferroelectric memory device,
the surface-modifying may be formed on an entire surface of the base and the first electrode, and selectively removed in a region which becomes the first region to form the surface-modifying film only in the second region.
(11) In this method of manufacturing a ferroelectric memory device,
the first electrode may be formed on a surface of the base,
the ferroelectric film may by formed on the first electrode,
the first region may be formed on an upper surface of the ferroelectric film,
the second region may be formed on surfaces of the base and the ferroelectric film excluding the upper surface of the ferroelectric film, and
the second electrode may be formed in the first region by forming a layer of an electrode material on the base on which the first electrode and the ferroelectric film are formed.
This enables the electrode material to be selectively formed on the upper surface of the ferroelectric film.
(12) In this method of manufacturing a ferroelectric memory device,
the step of forming the ferroelectric film may comprise:
a formation of a layer of an energy sensitive ferroelectric material on the base and the first electrode; and
a provision of energy to the formed ferroelectric material, thereby removing the ferroelectric material excluding a region which becomes the ferroelectric film.
This allows the ferroelectric film to be easily formed.
(13) In this method of manufacturing a ferroelectric memory device,
the upper surface of the ferroelectric film may be exposed in the first region, and
a surface of the second region may be a surface-modifying film of which affinity to the electrode material is lower than an affinity of the exposed surface of the ferroelectric film in the first region.
According to this configuration, affinity to a material for forming the electrode material in the first region can be relatively increased by decreasing the affinity to a material for forming the electrode material in the second region.
(14) This method of manufacturing a ferroelectric memory device may further comprise a step of removing the surface-modifying film after forming the second electrode.
(15) In this method of manufacturing a ferroelectric memory device, the surface-modifying film may be formed on an entire surface of the first electrode and the ferroelectric film, and selectively removed in a region which becomes the first region to form the surface-modifying film only in the second region.
(16) In this method of manufacturing a ferroelectric memory device,
a field effect transistor may be provided with a gate electrode, a source region, and a drain region which are formed on the base, and
the ferroelectric memory device may have a structure in which the first region corresponds to the electrode section connected to at least one of the source region and the drain region.
(17) In this method of manufacturing a ferroelectric memory device, a material for forming at least one member of the capacitor section may be selectively deposited in the first region by providing a material for forming the at least one member of the capacitor section using vapor phase growth.
Vapor phase growth is a process for supplying a material to be deposited in a vapor phase.
(18) In this method of manufacturing a ferroelectric memory device, the vapor phase growth may be chemical vapor deposition and a selective deposition process may be carried out in the first region.
(19) In this method of manufacturing a ferroelectric memory device, the second region may be formed above the first region.
(20) In this method of manufacturing a ferroelectric memory device which may comprise two or more the first regions,
a partition member may be formed between the first regions, and
the second region may be formed on the partition member.
According to this configuration, since the first regions are separated by the partition member, a problem in which the material for the ferroelectric film or the second electrode adheres to the side of the first electrode, or the material for the second electrode adheres to the side of the ferroelectric film can be prevented.
(21) In this method of manufacturing a ferroelectric memory device,
the partition member may be formed on the base, and
the second region may be formed at least on a surface of the partition member opposite to the base.
(22) In this method of manufacturing a ferroelectric memory device, the thickness of the partition member may be equal to or greater than the thickness of the capacitor section.
This prevents unnecessary material from adhering to the side of the capacitor section.
(23) This method of manufacturing a ferroelectric memory device may further comprise a step of removing the partition members.
(24) The present invention also provides a method of manufacturing a ferroelectric memory device provided with a capacitor section having a structure in which a base, a first electrode, a ferroelectric film, and a second electrode are deposited, the method comprising the steps of:
forming, on a surface of the base, a first region having surface characteristics allowing a material for forming at least one of the first electrode, the ferroelectric film, and the second electrode of the capacitor section to be preferentially deposited, and a second region having surface characteristics allowing a material for forming at least one member of the capacitor section to be less deposited than the first region, and formed above the first region; and
providing a material for forming at least one member of the capacitor section to selectively form the member in the first region.
According to the present invention, the first region and the second region are formed on the surface of the base. At least one member of the capacitor section can be selectively formed in the first region, but is less formed in the second region. Therefore, at least one of the first electrode, the ferroelectric film, and the second electrode can be formed without etching. In particular, degradation of the ferroelectric film can be reduced by applying the present invention when forming the first electrode and the second electrode, thereby easily achieving miniaturization of the device.
(25) In this method of manufacturing a ferroelectric memory device,
the surface of the base may be exposed in the first region, and
a surface of the second region may be a surface-modifying film of which affinity to the materials for forming the members of the capacitor section is lower than an affinity of the exposed surface in the first region.
(26) This method of manufacturing a ferroelectric memory device may further comprise a step of removing the surface-modifying film after forming at least one of the first electrode, the ferroelectric film, and the second electrode.
(27) A ferroelectric memory device according to the present invention is manufactured using the above method.
(28) A ferroelectric memory device according to the present invention comprises:
a base having a first region and a second region;
a first electrode formed in the first region;
a ferroelectric film formed on the first electrode; and
a second electrode formed on the ferroelectric film,
wherein the second region has surface characteristics allowing a material for forming at least one of the first electrode, the ferroelectric film, and the second electrode to be less deposited than a surface of the first region.
(29) In the ferroelectric memory device, the second region may be formed above a surface of the first region of the base.
(30) A ferroelectric memory device according to the present invention comprises:
a first electrode formed on a base;
a ferroelectric film formed on the first electrode; and
a second electrode formed on the ferroelectric film,
wherein the base and the first electrode have surface characteristics allowing a material for forming the second electrode to be less deposited than a surface of the ferroelectric film on which the second electrode is formed.
(31) In this ferroelectric memory device, a transistor connected to at least one of the first electrode and the second electrode may be formed on the base.